This invention relates to an apparatus and method for forming a body by deposition of a weld material.
The formation of components for aerospace engines can be carried out by any of several techniques involving deposition of a weld material. These techniques utilise an apparatus including two electrodes, the first electrode being held in a welding head to which is fed a supply of a metal wire constituting the weld material. The second electrode is in the form of a substrate or foundation upon which the weld material is to be deposited to form the component. The foundation may be in the form of a metal plate. A supply of an inert gas is fed to the welding head during its operation.
When the welding head and the foundation are connected to a supply of electricity, an arc is formed in the inert gas which melts the metal wire and a small region of the material forming the foundation. The metal is then deposited onto the foundation in a controlled manner. The welding head is mounted on a robotic arm and the foundation is mounted on a movable turntable. By controlling the movement of the arm and the turntable, the metal can be deposited on the foundation in order to form components of any desired shape.
One such method of forming components involves providing the welding head with a permanent electrode and also providing a separate metal wire to the welding head, the metal wire constituting the weld material. This method is generally known in the art as tungsten inert gas welding which is generally shortened to TIG welding. Although tungsten is commonly used, it will be appreciated by those skilled in the art that other suitable materials could be used as the electrode.
Another such method involves the use of a sacrificial electrode in the welding head. With this arrangement, the metal wire which provides the weld material also constitutes the electrode and is fed through the welding head. This method is generally known in the art as metal inert gas welding, which is generally shortened to MIG welding.
According to the invention there is provided a method of forming a body by deposition of a weld material, the method including the steps of:
providing a welding head;
providing a support member upon which the body is to be formed;
supplying a weld material to the welding head, the weld material to be deposited on the support member; and
connecting the support member and the welding head to a supply of electricity to form an arc between the welding head and the support member or the body to melt the material, the method further including the steps of:
manipulating the support member and the welding head relative to one another to deposit material to form a first wall;
manipulating the support member and the welding head relative to one another to deposit material to form a second wall extending from and angled to the first wall; and
manipulating the support member and the welding head relative to one another to deposit material to form a third wall joining the first two walls to form a hollow section body.
Each wall may be axi-symmetrical. The first wall may be substantially cylindrical. The second and third walls may be generally frustoconical. The hollow section body may be generally annular. The hollow section body may be for forming part of a casing structure for a gas turbine engine.
Preferably the electrical supply is controlled such that during the formation of each wall, the current is higher during the formation of a proximal base part of the wall than it is during the formation of a mid part of the wall, such that the base part of the wall is broader than the mid part of the wall.
Preferably the electrical supply is controlled such that during the formation of each wall, the current is higher when forming a distal part of the wall than when forming the mid part of the wall, such that the distal part of the wall is broader than the mid part of the wall.
Preferably during the formation of the first wall, the support member is oriented substantially horizontally and the welding head substantially vertically, such that a substantially vertical first wall is produced.
Following the formation of the first wall, preferably the support member is tilted to an angle of between 10xc2x0 and 50xc2x0 to the horizontal. The second wall may then be deposited onto the first wall at an angle thereto. The support member and the welding head may be manipulated such that the first wall is held at an angle to the horizontal and the second wall is built up on the first wall. The second wall may be built up substantially vertically.
Following formation of the second wall, the support member may be manipulated such that the second wall is angled to the vertical. The first wall may be substantially horizontal. The support member and the welding head may then be manipulated to form the third wall, joining the first and second walls.
The method may include the step of further producing fourth and optionally subsequent walls, the walls together forming a hollow section body.
During the formation of an angled wall, the welding head may initially be oriented substantially vertically. As the wall is built up, the orientation of the head may be gradually altered such that its angle to the vertical gradually increases.
The method may include the steps of:
initially producing a two or three dimensional model of the body to be formed, using computer aided design and computer aided manufacturing software;
taking into account the geometry of the support member and of the means for manipulating the welding head, producing a defined path for the welding head to follow;
using the above information to produce a welding program in which each positionable point for the welding head is defined; and
utilising the above program to control the means for manipulating the welding head.
Preferably the method includes the use of a robot for manipulating the welding head, the robot preferably having six degrees of freedom of movement.
An embodiment of the invention will now be described for the purpose of illustration only with reference to the accompanying drawings in which: